Measuring flow through pipes has a number of uses in various industries and can be achieved in a number of ways. In a simple form, such as shown in FIG. 1A, for example, a pipe can be fitted with an orifice plate of known orifice size in the pipe's bore. Upstream and downstream pressure measurements across the orifice plate can then be used to measure the flow.
A pipe can alternatively be fitted with wedged restriction formed in the pipe's bore. As shown in FIG. 1B, for example, a wedge flowmeter is one type of meter with this configuration. A wedge ratio for the flowmeter is defined by d/D where d is a wedge opening height and D is a nominal pipe diameter. The wedge restriction is typically V-shaped at an angle to help in measuring viscous fluids. A first pressure gage can measure an upstream pressure measurement, while a second pressure gage can measure a downstream pressure measurement, subject to the pressure drop from the orifice plate or wedged restriction.
As shown in FIG. 1C, another configuration has a throat formed in the pipe's orifice. Pressure from a pressure tap upstream of the throat's restriction can be compared to pressure from a pressure tap at the throat's restriction. In yet another alternative shown in FIG. 1D, a cone can be positioned in the pipe's bore. Pressure from a pressure tap upstream of the cone can be compared to pressure from a conduit to the cone inside the pipe's bore.
In a drilling environment, drilling chokes are used in several applications to control the flow of production medium or drilling fluids. For example, well control for circulating a “kick” or underbalanced and near-balanced drilling applications often require the use of one or more drilling chokes. In addition, drilling chokes are useful for conventional well control issues involving exploration wells and drilling over-pressured zones, well testing operations and well clean ups that require flow control of the wellbore fluid to produce reliable test results.
In the drilling environment, flow measurement is a necessary element for performing various drilling operations, such as in well control operations. Devices, such as the wedge flowmeter, the V-cone flowmeter, or the like, may not be suitable for all drilling operations, especially those operation involving higher mud pressures. For this reason, the flow measurement in managed pressure drilling (MPD) is typically made using a Coriolis flowmeter. Using one of these dedicated Coriolis flowmeters in the drilling system can be expensive. Additionally, current Coriolis meters have pressure limitations of 1,500 to 2,800 psi. Drilling equipment typically requires pressures in the 5,000 to 10,000 psi range.
In drilling operations, maintaining the bottom hole pressure using a hydraulic model requires calculations that rely on knowing the density of the flow. However, measuring flow and density can be challenging in drilling environments. In general, the measurements from a Coriolis flowmeter in a drilling system can be used as a densitometer and a flowmeter.
Although effective, Coriolis flowmeters can be costly and can have lower pressure ratings than desired for some implementations. Other than a Coriolis flowmeter, existing density measurements rely on nuclear devices, gravity, etc. along with sensitive pressure sensors that have a low pressure rating. Therefore, these other techniques for measuring density are less favorable. This can be especially true when performing managed pressure drilling on a land-based rig as opposed to offshore. For land based rigs, for example, flow measurement for managed pressure drilling can be very useful and needed. However, adding a dedicated flowmeter, such as a Coriolis flowmeter, may not be the best solution.
The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.